Electromagnetic device



Nov. 22, 1932. P, N. MARTIN ELEGTROMAGNETXC DEVICE Filed Aug. 23, 1952 Fig. 2.

INVENTOR. H Paul M Marina BY HIS .-1TTORNEY.

Patented Nov. 22, 1932 1 UN STATES PATENT OFFICE PAUL N. IJARTIN, OF SWISSVALII, PENNSYLVANIA, ASSIGNOR TO THE UNIGN SWITCH &.

SIGNAL CGMPAECY, OF SVJISSVALE, PENNSYLVANIA, A CORPORATION OF PENN- SYLVANIA ELECTROMAGNETIC DEVICE Application filed August 23, 1932. Serial No. 630,076.

My invention relates to electromagnetic dethis characteristic tends to make the enerrices oi the type comprising an eleetromaggizaticn value for pick up of the armature net and an armature coacting therewith and high and the energization value for release piiotally lll'ill iittl on an a (is. which is at a Without contact pressure quite low, it is un- 5 greater drtanee from one pole than from the desirable when the electromagnetic device is 5 other. (hie ohjert o'l'niy nvention the conused as part of a track relay for a railway strnrtion of a magnet of this kind in such signal system. By constructing the device manner as to improve the torque eharacterisin the manner described, however, I have reties of the de\ il'c. duced the steepness of the torque curve and I will (l(' -('1lll! one form of device emhodyhave therefore improved the characteris- 60 ing my iilY-LIltitlil. and will then point out tics of the device for use as a track relay. the novel l'eaturts thereof n the claim. The decrease in torque with increase of in the illL'Uiillfilllj'lllfi drawing. Fig. l is a armature opening is caused mainly by the inview Fllnk'filllg' in front elevation one form of crease in reluctance of the air gaps between lltl'ilolilllfilli'lll device euihoilying my invcnthe armature and the poles and the conse- 65 tion. Fig. :2 i a bottom view of the device qucnt reduction in magnetic flux. The reshown in Fig. l. luctance of the front air gap B increases more tnnnhir reference characters refer to SllIllrapidly than that of the rear air gap A as lar part in earl: of the news. the armature opening mereases. because air lleterring to the drawing. the reference gap B is at a greater radius than air gap A Z character Bl dcisignates an electronnignct from the pivotal point 4. This rapid incomprising two parallel cores 2A and 2B crease in reluctance of air gap B causes the eonnerted at their upper ends hy a llaelcstrap steep torque curve when the two air gaps are i (ore 2A is provided with a pole (3A. and equal in area. By making the area of the core 2B is provided with a pole (ill. In acfront air gap B larger than that of air gap llll'lltlilit with my invention the area of the A. the reluctance of air gap B at small 0penpole (3A is eonshlerahly less than the area ings is decreased to a small part of the total of the pole (Ill. (carting with the magnet reluctance of the two air gaps in series. Al-

M is an armature pivotally mounted on an though the reluctance of gap B will still in- 30 axis 4 which axis is adiacent the outer edge crease rapidly with increase in armature 89 of the smaller core (at and in perpendicular opening, its effect on the total reluctance will to the general plane of the magnet M. The he reduced. For example. I will assume that closed or energized osition of the armature the two poles. and therefore the two air gaps,

(l limited hr a core pin 5 n the face of the are of equal areas, and that the total relucpole (ill. ln order to simplil'v the following t mee of the two gaps in series, with the armaexplanation. I will refer to the air gap heture in closed position. is R. that the reluc tween the pole (Hi and the armature C as the tance of the rear air gap A is RA=1/21?, air gap A. and I will refer to the air gap heand that the reluctance of the front air gap tween th pole fill and the arn'iature C as the B is 1 ?B 1/2ll As the armature moves air gap B. away from its closed position, RB increases Ordinarily, electromagnetic devices of the much more rapidly than RA, so that when type to which this invention relates are eon- RA has doubled and is therefore equal to :-lIH('l(il with the two poles of the same size. 2 l/2R=R, RB may have increased three and when so roustriu-ted the curve plotted tim as uch and is thus equal to 3B. The

45 lretweeu torque exerted on the armature and total reluctance will then he R+3R=4R. the amount of armature opening. for con- Considering now the structure shown in stant a mpere turn energisation. is very steep. the drawing, I will assume before that the That is to say. the torque large for a small total reluctance of the two air gaps in series armature ()l)fillll,1'.l)l1i decreases very rapidly with the armature in its closed position is 50 the armature opening increases. Since equal to R, but that the reluctance of the rear gap A is 2/33 and that the reluctance of the front gap B is 1/31 \Vhen the armature has moved away from its closed position far enough to double RA so that [KA 2X2/3P 4/3R, and assuming again that RB increases three times as fast as BA, BB will then equal 3 2 1/3R=2R. The total reluctance will then be 4/3R+2R, which is equal to 3 1/3R instead of 1B as before. Since the flux Varies inversely as the reluctance and the torque varies as the square of the flux, it is evident that as the armature opens the torque of a device constructcd in accordance with my invention decreases much less rapidly than that of a device constructed in the usual manner.

Although I have herein shown and described only one form of electromagnetic device embodying my invention, it is understood that various changes and modifications may be made therein within the scope of the appended claim without departing from the spirit and scope of my invention.

Having; thus described my invention, what I claim is:

An electromagnetic device comprising an electromagnet having two poles of different areas, and an armature coacting with said poles and pivotally mounted on an axis which is located adjacent the outer edge of the pole of smaller area.

In testimony whereof I afiix my signature.

PAUL N. MARTIN. 

